Sealable repulpable valve bag and method of assembling

ABSTRACT

A valve tube assembly for a repulpable bag having a valve end portion includes, in an exemplary embodiment, a valve tube member formed from a repulpable paper material, wherein the valve tube member includes a first end, a second end, an inside surface, and an outside surface, and a water dispersible hot melt adhesive layer deposited on at least a portion of the inside surface adjacent the first end by a timed application, with a remainder of the inside surface being free of the water dispersible hot melt adhesive. The valve tube member is sized to extend into the valve end portion of the repulpable bag with the second end positioned inside the repulpable bag.

BACKGROUND OF THE INVENTION

The field of the invention relates generally to paper bags, and moreparticularly to a sealable repulpable valve bag.

A valve bag is a container having a body portion of substantiallytubular configuration, which has an outer layer of at least one ply, andan inner layer of at least one ply. The plies may be made from arelatively stiff and sturdy paper material. The first end of the bag(usually the end the ultimate consumer opens) may be cut in a steppedend pattern, folded over and sealed, to form what is called apinch-bottom bag. Alternatively, the first end may be formed with twosets of flaps, arranged in opposed pairs. The first pair of opposedflaps are folded inwardly toward one another (in-folded flaps). The twoother flaps (outer flaps), typically oriented perpendicular to thein-folded flaps, would be folded over the already folded flaps and gluedin place to close that end of the bag, such that when the bag is filled,the bottom of the bag will assume a square-bottomed shape.

Rather than leave the second end of the bag completely open for fillingthe valve bag, the bag can be filled with the second end of the bagsubstantially closed, when a valve is provided. In a valved bag, thesecond end is closed using in-folded flaps as described above. Thetubular bag form is flattened somewhat, and the in-folded flapscorrespond to the two opposite “short” sides of the bag. The in-foldedflaps may or may not overlap. The outer flaps, which correspond to the“long” sides of the bag, are then folded over one another, and glued toeach other. In addition, one of the in-folded flaps may be glued to theouter flaps. The remaining in-folded flap is not glued to either theouter flaps or the other in-folded flap, and so a channel can be formed,upon outward deflection of the glued and overlapped outer flaps, leadingto the interior of the bag. If the in-folded flaps overlap, the valve islocated on the side of the “under” flap. Filling can be accomplished bythe insertion of an appropriately configured nozzle, which will extendto the gap between the in-folded flaps, to drop material into theinterior of the bag, or if the in-folded flaps overlap, the nozzle willproject under the “over” flap and into the bag far enough to clear the“under” flap and access the interior of the bag.

There are two general kinds of valved bags, those which cannot besealed, and those which can be sealed. The bag described above, is anunsealed bag, as once filling has been accomplished, there can be nofurther gluing, or other sealing procedure which can be done withoutpotentially disturbing or contaminating the contents of the bag, sincethe gap between the outer flaps and the unglued in-folded flap wouldhave to be re-opened to place a seal between them.

In some instances, it is desirable to be able to fully seal the bag,after filling by the valve method. In such instances, an outwardlyextending valve tube can be used in sealing the bag. In such a bag, thevalve extension is a tube, formed from the stiff paper bag materialpreviously described. The tube is positioned inside the valve area, soas to extend outwardly, well past the side of the bag, and inwardly, toa position substantially even with the inner edge of the valve sidein-folded flap. The entire inner surfaces of the tube are coated with anadhesive/sealing material, such as a heat activatable glue, or anadhesive which may be activated by ultrasonic means. During the fillingprocess, the valve tube is opened, and a filling nozzle is inserted. Dueto the stiffness of the combined paper and the adhesive/sealingmaterial, the valve tube may tend to remain slightly open, even afterremoval of the filling nozzle.

Once filled, the valve is typically flattened, and the end of the valvetube is sealed, either by application of heat or ultrasonic vibrations,to activate the sealing adhesive. In other valve tube bag constructions,a tab on the “upper” portion of the outwardly extending tube extendsfurther than the “lower” portion, and instead of relying upon anadhesive lined tube, an applicator puts a hot melt glue on the undersideof the tab, and a wiper presses the valve tube downward against the sideof the filled bag, simultaneously closing the bag and affixing the tubeagainst the bag side.

In the paper manufacturing industry, it is well known to use dryadditives, such as the whitening agent titanium dioxide, which areshipped in large paper bags which must be individually opened and dumpedinto the pulp mixture. Typically such additives are added to an ambienttemperature mixture, for example, 60° F. to 80° F. Some dry additivesthat are used in the paper making industry are packaged in “beater bags”which are substantially closed across the top, using conventional watersoluble bag manufacturing adhesives, except for a fold-in spout throughwhich the bag is filled. In the case of “beater bags”, the entire bag isthen added to the pulp mixture for making a batch of paper. The bagdisintegrates, becoming incorporated into the pulp mixture along withits contents. Such “beater bags” have the disadvantage, however, thatfilling through the spout is difficult and that after filling andfolding in of the spout, the bag remains unsealed and therefore allowsfor leakage of the contents during shipping and handling. It is known toutilize hot melt adhesives to seal bags of dry bulk chemicals but theknown adhesives used for this purpose have been incompatible with thepulp mixture and can cause discoloration or spotting of the manufacturedpaper, or can contaminate the dry chemicals. It is also known to apply aheat activated adhesive to the entire inner surfaces of the spout, butsuch adhesives are also incompatible with the pulp mixture, or sealprematurely when they are exposed to moisture from the sealing of thebottom of the bag.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a valve tube assembly for a repulpable bag having a valveend portion is provided. The valve tube assembly includes a valve tubemember formed from a repulpable paper material, wherein the valve tubemember includes a first end, a second end, an inside surface, and anoutside surface. A water dispersible hot melt adhesive layer isdeposited on at least a portion of the inside surface adjacent the firstend by a timed application, with a remainder of the inside surface beingfree of the water dispersible hot melt adhesive. The valve tube memberis sized to extend into the valve end portion of the repulpable bag withthe second end positioned inside the repulpable bag.

In another aspect, a method of assembling a valve tube assembly for arepulpable bag having a valve end portion is provided. The methodincludes providing a roll of repulpable paper material having an insidesurface and an outer surface, applying a water dispersible hot meltadhesive to at least a portion of the inside surface of the repulpablepaper material, and cutting the repulpable paper material to apredetermined length to form a valve tube blank. The valve tube blankincludes a first end and a second end, wherein the water dispersible hotmelt adhesive applied to the inside surface is located adjacent thefirst end of the valve tube blank.

In another aspect, a method of assembling a sealable repulpable valvebag is provided. The repulpable bag includes a front wall, a rear wall,opposing side walls, and a valve end portion. The method includesproviding a repulpable valve bag having a first outer flap, an opposingsecond outer flap, a first in-folded flap and a second in-folded flap,and assembling a valve tube assembly. The valve tube is assembled byproviding a roll of repulpable paper material having an inside surfaceand an outer surface, applying a water dispersible hot melt adhesive toat least a portion of the inside surface of the repulpable papermaterial, cutting the repulpable paper material to a predeterminedlength to form a valve tube blank, with the valve tube blank including afirst end and a second end, wherein the water dispersible hot meltadhesive applied to the inside surface is located adjacent the first endof the valve tube blank. The method also includes forming a tubularvalve tube assembly from one valve tube blank wherein the inside surfaceof the repulpable paper material forms the inside surface of the valvetube assembly. The method further includes attaching the valve tubeassembly to the first in-folded flap so that the first end of the valvetube assembly is located outside the repulpable valve bag and the secondend of the valve tube assembly is located inside the repulpable valvebag, and folding the first and second outer flaps and attaching theouter flaps to each other, the valve tube assembly, and the secondin-folded flap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a repulpable valve bag in accordancewith an embodiment of the present invention.

FIG. 2 is a side elevation in section, of the repulpable valve bag shownin FIG. 1.

FIG. 3 is a plan view of a roll of paper material for forming the valvetube shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

A sealable repulpable valve bag that can be used in paper makingprocesses is described below in detail. The repulpable bagdisintegrates, becoming incorporated into the pulp mixture along withits contents when added to a pulp mixture used for making a batch ofpaper. The repulpable bag utilizes a water dispersible hot melt adhesivewhich may be activated by heat and/or ultrasonic energy to seal thebag's valve tube. The water dispersible hot melt adhesive and any otherwater soluble adhesives used to manufacture the valve bag are compatiblewith the pulp mixture used in paper making processes.

A repulpable valve bag 50 capable of being sealed is shown in FIGS.,1-3. In an exemplary embodiment, valve bag 50 includes opposing sidewalls 52 and 54, opposing in-folded flaps 56 and 57, and outer flaps 58and 60. Bag 50 is fabricated from three layers of bag material, outerlayer A, and inner layers B and C. In alternate embodiments, bag 50 maybe formed with greater or fewer than three layers. Layers A, B, and Care adhered together, at least in portions, by layers of adhesive D. Inorder to facilitate filling and subsequent sealing of bag 50, a valvetube 62 is provided. Valve tube 62 is an integral unit that includes avalve tube member 64 formed from a repulpable paper material and issecured in bag 50 during manufacture. Valve tube member 64 has a uniformlength, from its inside end 61, to its outside end 63, around itscomplete circumference. Valve tube member 64 is affixed to in-foldedflap 56 and outer flaps 58 and 60 by adhesive layer D. Adhesive layer Dis formed from a water soluble starch based adhesive that is compatiblewith pulp mixtures used in paper making processes. Valve tube member 64is coated on its interior surface 65 along outside end 63 with anadhesive material 66. Adhesive material 66 is a water dispersible hotmelt adhesive which may be activated by heat and/or ultrasonic energy.Adhesive material 66 should be compatible with pulp mixtures used inpaper making processes. Any suitable water dispersible hot melt adhesivematerial may be used, for example, a water dispersible polyamide hotmelt adhesive, NP-2068, commercially available from H. B. Fuller, St.Paul, Minn.

Referring also to FIG. 3, valve tube member 64 is formed from acontinuous roll of paper stock 70. Valve tube member 64 is cut to lengthalong cut lines 72. Hot melt adhesive material 66 is deposited onadjacent outside end 63 of valve tube member 64 along cut line 72.Because cut line 72 defines outside end 63 and inside end 61 of adjacentvalve tube members 64, the timing of the adhesive application to outsideend 63 as the continuous roll of paper stock 70 moves past an adhesiveapplicator is controlled to prevent the application of adhesive material66 to inside end 61 of valve tube member 64 of an adjacent valve tubemember 64 along cut line 72.

If adhesive material 66 is applied to both inside end 61 and outside end63, valve tube member 64 might be sealed at inside end 61 during theactivation of adhesive layer D used to attach valve tube member 64 toin-folded flap 56 and outer flaps 58 and 60. In addition, if adhesivematerial 66 extends too far inwardly from outside end 63, adhesivematerial 66 can pick up moisture from adhesive layer D and prematurelyseal valve tube member 64. Thus, adhesive material 66 is strategicallyapplied to outside end 63 of valve tube member 64. In the exemplaryembodiment, adhesive material 66 extends approximately one-quarter inch(⅛″) plus or minus one-eighth inch (±⅛″) to approximately three inches(3″) plus or minus one-eighth inch (±⅛″) or beyond from outside end 63of valve tube member 64. More specifically, in the exemplary embodiment,adhesive material 66 extends approximately three-quarter inch (¾″) plusor minus one-eighth inch (±⅛″) to approximately one and one-quarterinches (1¼″) plus or minus one-eighth inch (±⅛″) from outside end 63 ofvalve tube member 64. The distance of adhesive material 66 from outsideend 63 towards inside end 61 may be variable between production lots.Final dimensions of bag 50 and valve tube member 64 may also be variablebetween production lots, thus causing the need for different areas ofadhesive material 66 coverage extending from outside end 63 to insideend 61. In some configurations, adhesive material 66 could extend towardinside end 61 where moisture from adhesive layer D may prematurely sealvalve tube member 64. The premature seal point can vary betweenproduction lots. For most, but not all applications, adhesive materialextends approximately one-quarter inch (⅛″) plus or minus one-eighthinch (±⅛″) to approximately three inches (3″) plus or minus one-eighthinch (±⅛″) from outside end 63 of valve tube member 64.

After paper stock 70 is formed as a continuous roll with hot meltadhesive material 66 being strategically positioned on outside end 63,each valve tube member 64 included on the continuous roll of paper stock70 is folded, and cut into an individual valve tube member 64 by anautomated bag forming machine. The bag forming machine then inserts andadheres folded valve tube member 64 to bag 50. When forming bag 50, thebag forming machine automatically cuts paper stock 70 along cut lines 72to form individual valve tube member 64. Each valve tube member 64 isfolded, cut and inserted into partially formed bag 50 and is properlypositioned on in-folded flap 56 of bag 50. Once valve tube member 64 ispositioned and adhered to in-folded flap 56, the bag forming machinethen folds outer flaps 58 and 60, which in turn causes valve tube member64 to be further adhered to bag 50.

More specifically, upon cutting paper stock 70 along cut lines 72, aplurality of valve tube member blanks 73 are formed. The bag formingmachine for forming bag 50 includes an electronic drive system whichcontrols the tension of paper stock 70 as the material is folded intovalve tube member 64 and fed into a cutting device. An electroniccontrast sensor system measures contrast differences between the valvetube member 64 and the adhesive material 66, which enables the bagforming machine to properly cut each valve tube member 64. In theexample embodiment, the contrast sensor systems measures the contrastbetween adhesive material 66 and paper stock 70. In another embodiment,a fluorescent additive is added to adhesive material 66 such that thefluorescent additive is detectible by a fluorescent sensor fordetermining the proper location for cutting valve tube member 64. Inanother embodiment, a colorant additive is added to adhesive material 66such that the colorant additive is detectible using a reflectancemeasurement for determining the proper location for cutting valve tubemember 64.

An individually folded and cut valve tube member 64 is then positionedby the bag forming machine on in-folded flap 56. The position of valvetube member 64 on in-folded flap 56 is controlled by the contrast sensorand the electronic drive system of the bag forming machine. Valve tubemember 64 is formed into a substantially tubular shape by affixing afirst side edge 74 to a second side edge 76 in an overlapped arrangementwith adhesive layer D.

In the process of making bag 50, valve tube member 64 is positioned andaffixed onto in-folded flap 56 of bag 50 before outer flaps 58 and 60are folded down and glued into place. Valve tube member 64 is furtherattached to bag 50 by folding outer flaps 58 and 60 into contact withvalve tube member 64. Adhesive layer D is applied to the upper side ofvalve tube member 64, among other areas, and outer flaps 58 and 60 arefolded over each other and also secured to in-folded flap 57.

Filling of bag 50 is accomplished by inserting a nozzle into a valvepassage 78 and bag filling material is discharged into the interior 80of bag 50. Upon completion of filling, bag 50 is sealed by sealing valvepassage 78 closed. In one embodiment, bag 50 is sealed by applying heatto adhesive material 66. In another embodiment, an ultrasonic generatorhead 68 and anvil 82 combination is positioned adjacent to outside end63 of valve tube member 64. Outside end 63 of valve tube member 64 ispositioned between generator head 68 and anvil 82, which then cometogether, closing outside end 63, and applying ultrasonic energy toactivate adhesive material 66 to seal the valve tube member 64.

While the invention has been described in terms of various specificembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theclaims.

1. A valve tube assembly for a repulpable bag having a valve endportion, said valve tube assembly comprising: a valve tube member formedfrom a repulpable paper material, said valve tube member comprising afirst end, a second end, an inside surface, and an outside surface; anda water dispersible hot melt adhesive layer deposited on at least aportion of said inside surface adjacent said first end by a timedapplication, a remainder of said inside surface being free of said waterdispersible hot melt adhesive; said valve tube member sized to extendinto the valve end portion of the repulpable bag with said second endpositioned inside the repulpable bag.
 2. A valve tube assembly inaccordance with claim 1 wherein said water dispersible hot melt adhesivelayer comprises a water dispersible hot melt polyamid adhesive, saidwater dispersible hot melt polyamid adhesive repulpable and dispersibleinto a pulp mixture of a paper making process.
 3. A valve tube assemblyin accordance with claim 1 wherein said valve tube member comprises avalve passage extending therethrough.
 4. A method of assembling a valvetube assembly for a repulpable bag having a valve end portion, saidmethod comprising: providing a roll of repulpable paper material havingan inside surface and an outer surface; applying a water dispersible hotmelt adhesive to at least a portion of the inside surface of therepulpable paper material; and cutting the repulpable paper material toa predetermined length to form a valve tube blank, the valve tube blankcomprising a first end and a second end, wherein the water dispersiblehot melt adhesive applied to the inside surface is located adjacent thefirst end of the valve tube blank.
 5. A method in accordance with claim4 wherein applying a water dispersible hot melt adhesive to at least aportion of the inside surface of the repulpable paper material comprisestiming the application of the water dispersible hot melt adhesive sothat the water dispersible hot melt adhesive is applied adjacent apredetermined cut line that defines the first end of one valve tubeblank and the second end of an adjacent valve tube blank, wherein thewater dispersible hot melt adhesive is not applied to the second end ofthe adjacent valve tube blank.
 6. A method in accordance with claim 4further comprising forming a tubular valve tube assembly from one valvetube blank wherein the inside surface of the repulpable paper materialforms the inside surface of the valve tube assembly.
 7. A method inaccordance with claim 6 wherein the inside surface of the valve tubeassembly defines a valve passage extending through the valve tubeassembly.
 8. A method in accordance with claim 6 wherein the valve tubeassembly formed from the valve tube blank is repulpable and dispersibleinto a pulp mixture of a paper making process.
 9. A method in accordancewith claim 4 wherein cutting the repulpable paper material to apredetermined length to form a valve tube blank comprises cutting therepulpable paper material to a length that permits one end of the valvetube assembly to be positioned inside the valve end portion of therepulpable bag while an opposing end of the valve tube assembly ispositioned outside the repulpable bag.
 10. A method of assembling asealable repulpable valve bag, the repulpable bag having a front wall, arear wall, and opposing side walls, and a valve end portion, said methodcomprising: providing a repulpable valve bag having a first outer flap,an opposing second outer flap, a first in-folded flap and a secondin-folded flap; assembling a valve tube assembly by: providing a roll ofrepulpable paper material having an inside surface and an outer surface;applying a water dispersible hot melt adhesive to at least a portion ofthe inside surface of the repulpable paper material; and cutting therepulpable paper material to a predetermined length to form a valve tubeblank, the valve tube blank comprising a first end and a second end,wherein the water dispersible hot melt adhesive applied to the insidesurface is located adjacent the first end of the valve tube blank; andforming a tubular valve tube assembly from one valve tube blank whereinthe inside surface of the repulpable paper material forms the insidesurface of the valve tube assembly; attaching the valve tube assembly tothe first in-folded flap so that the first end of the valve tubeassembly is located outside the repulpable valve bag and the second endof the valve tube assembly is located inside the repulpable valve bag;and folding the first and second outer flaps and attaching the outerflaps to each other, the valve tube assembly and the second in-foldedflap.
 11. A method in accordance with claim 10 wherein applying a waterdispersible hot melt adhesive to at least a portion of the insidesurface of the repulpable paper material comprises timing theapplication of the water dispersible hot melt adhesive so that the waterdispersible hot melt adhesive is applied adjacent a predetermined cutline that defines the first end of one valve tube blank and the secondend of an adjacent valve tube blank, wherein the water dispersible hotmelt adhesive is not applied to the second end of the adjacent valvetube blank.
 12. A method in accordance with claim 10 wherein the valvebag and the valve tube assembly formed from the valve tube blank isrepulpable and dispersible into a pulp mixture of a paper makingprocess.
 13. A method in accordance with claim 10 wherein providing arepulpable valve bag comprises providing a repulpable valve bag havingat least two layers of repulpable paper.
 14. A method in accordance withclaim 10 wherein the inside surface of the valve tube assembly defines avalve passage extending through the valve tube assembly.